Associations between common variants in GC and DHCR7/NADSYN1 and vitamin D concentration in Chinese Hans

Recent studies have identified common variants in or near GC, CYP2R1 and NADSYN1/DHCR7 to be associated with 25-hydroxyvitamin D [25(OH)D] levels in European populations. We aimed to examine whether these variants also influence 25(OH)D levels in Chinese. Seven common variants were successfully genotyped and tested for associations with plasma 25(OH)D levels in a population-based cohort of 3,210 Chinese Hans from Beijing and Shanghai. Six common variants at GC (rs4588, rs7041, rs2282679 and rs1155563) and NADSYN1/DHCR7 (rs3829251 and rs1790349) loci were all significantly associated with lower plasma 25(OH)D levels (-0.036 a parts per thousand currency sign beta a parts per thousand currency sign -0.076 per risk-allele, P a parts per thousand currency sign 5.7 x 10(-5)), while CYP2R1-rs2060793 showed a trend toward association with 25(OH)D levels in the Shanghai subpopulation (P = 0.08), but not in the Beijing subpopulation (P = 0.82). Haplotype-based association analyses of the four GC variants showed that only the haplotype that contained all risk-alleles (TACC) was significantly associated with lower plasma 25(OH)D levels (beta = -0.085, P = 2.3 x 10(-9)), while the haplotype containing the risk-alleles of rs4588 and rs2282679 (TATC) was marginally associated with lower 25(OH)D levels (beta = -0.054, P = 0.0562) when compared with GCTA haplotype carrying the four protective alleles. Most notably, conditional analyses showed that only GC-rs4588 and GC-rs2282679 (r (2) = 0.97) remained significantly associated with 25(OH)D concentrations (P a parts per thousand currency sign 1.9 x 10(-5)) after adjusting for the other two SNPs in GC. In conclusion, GC and NADSYN1/DHCR7 loci individually and collectively contribute to variation in plasma vitamin D levels in Chinese Hans.